Piston



Sept. 29, 1942. p KOCH v 2,297,655

' PISTON Filed July 2, 1941 jzazvrzczz Patented Sept. 1942 UNITED ST PISTON Paul F. Koch, Oak Park, Ill., assignor to Chicago Die Casting Manufacturing Company, a corporation of Illinois Application July 2, 1941, Serial No. 400,729

1 Claim.

There is in common use a type of door check in which there is fastened to a hinged door, near the hinge edge, a cylinder containing a piston from which projects a stem that strikes against the door casing as the door closes, thereby causing the piston to be driven back into the cylinder. The escape of air behind the piston is regulated, so that the backward movement of the piston is resisted and a braking effect on the closing movement of the door is created.

This old type of door check has several faults, and the primary object of the present invention is to overcome them.

One of the chief faults of the aforesaid door checks arises from the fact that the cup wash- .ers carried by the pistons soon become suffimatic door checks, due to the failure of cup washers to make effective seals between their pistons and surrounding cylinder walls, is found in other devices employing similar pistons and, therefore, the present invention may be said to have for its object to produce a simple and novel means I) for insuring an effective seal between any piston and a surrounding cylinder Wall throughout the stroke during which it is the intention that a cup washer on the cylinder shall bring about such a seal.

A further fault in pneumatic door checks of the old type to which I have referred is due to the striking of the outer end of the piston rod against the door frame, resulting in the marring of the frame and objectionable noise as the end of the piston rod is drawn across the surface of the frame, and a dragging effect which may cause the piston to bind within the cylinder. In one of its aspects, the object of the present invention is to prevent the occurrence of the objectionable conditions just noted.

The various features of novelty whereby my invention is characterized will hereinafter be pointed out with particularity in the claim; but, for a full understanding of my invention and of its objects and advantages, reference may be had to the following detailed description taken in connection with the accompanying drawing, wherein:

Figur 1 is a top plan view of a fragment of a 55 door and its casing, equipped with a recoil check embodying the present invention; Fig. 2 is a central longitudinal section through the recoil check, the section being taken on a horizontal plane; Fig. 3 is an end view of the recoil check, showing it attached to the door of which a fra ment appears in section; Fig. 4 is a side view of a fragment of the device; and 'Fig. 5 is an elevation of the block or shoe which is attached to the door frame in position to be engaged by the outer end of the piston rod forming part of the device.

Referring to the drawing, I represents a cylinder open at one end and closed at the other and which may conveniently be a die casting. The open end of the cylinder is closed by a capshaped cover 2 held in place by means of pins 3 projecting radially from the cylinder and adapted to be engaged with bayonet slots 4 in the cylindrical flange or wall of the cover or head. Within the cylinder is a piston 5, which may be of any usual or suitable construction as long as it contains a cup-shaped packing element 6 of leather or other flexible material whose cylindrical wall or flange surrounds the piston and projects somewhat beyond the inner or rear side of the piston; the web or bottom portion of the cup being suitably secured to the piston. The piston has an elongated hub 1 extending rearwardly therefrom. Extending through this hub and out through the head or cover member 2 of the cylinder is a sturdy piston rod 8 which is firmly fastened in any suitable way to the piston. Surrounding the hub, behind the piston, and loose F thereon, is a short sleeve 9 having at its inner or rear end a little peripheral flange l0. Surrounding the sleeve 9, in front of the flange on the latter, and prevented by the flange from slipping 01f the rear or inner end of the sleeve, is a round follower plate I l, in the form.of a thin, stiff disk, the marginal portion of which is deflected rearwardly somewhat, as indicated at l2, in order to give the follower the shape of a shallow flatbottomed dish. The follower is smaller in diameter than the interior of the cylinder, so that the curved marginal portion I2 may act as a short frusto-conical wedge that enters the mouth of the cup washer and spreads the cylindrical wall or flange thereof into intimate contact with the surrounding cylinder wall whenever a proper pressure is exerted. Obviously, if the piston is pushed in sharply while the air cannot escape freely from behind the piston, the pressure of the confined air acts directly on the follower in a manner to force it toward the piston and cause the flexible sealing element to spread. Since the rear end of the cylinder is closed, the air cannot escape unless means are provided for this to happen. In the arrangement shown, there is an outlet port l4 leading from the interior of the cylinder through the rear head; this port being controlled, as is customary, by a little valv l5 of the needle valve type. Whatever the setting of the valve may be, the air cannot escape rapidly enough to avoid the building up of pressure behind the piston whenever the piston is pushed back sharply and, therefore, the floating follower always comes into play to insure the presence of an effective seal between the piston and the cylinder whenever there is need for one. The valve, of course, controls the rate at which the air can leave the cylinder and, therefore, when the device is acting as a door check, controls the rate of deceleration of the closing movement of the door,

On the return stroke of the piston it is best that the piston be loose in the cylinder and be permitted to move freely. The piston is driven through its return stroke by the usual spring 16 arranged behind the same within the cylinder. Therefore, as soon as the condition which causes the piston to be held in the closed end of the cylinder ceases to exist, the spring begins to force the piston forwardly. This may resultin the creation of a partial vacuum behind the piston, so that if the follower has not already Withdrawn from the position in which it spreads the sealing element, it will now do so and the pressure of the sealing element against the cylinder wall is eliminated.

Since the short sleeve or collar 9 is loose on the hub of the piston, and could therefore slide off at the rear end of the same unless restrained in some manner, I make the front end of the spring large enough to surround the hub and exert its pressure against the rear edge of the short sleeve or collar and thus yieldingly hold the short sleeve or collar on the hub. The spring does not necessarily act upon the follower, and

it preferably does not; the follower being of the fioa-ting type and free to move lengthwise of the sleeve or collar. In Fig. 2 of th drawing the sleeve or collar is shown as having been pushed far enough back to engage with the rear face of the body of the piston, while the follower engages with the flange H] on the sleeve or collar and just barely makes contact with the leather or other washer. There is a considerable gap between the follower and the rear face of the body of the piston, so that the air pressure behind the follower, during a braking stroke of the piston not only serves to push the follower forward far enough to spread the sealing element, but may push it forward farther and farther effectively to achieve this result, as wear takes place and the material of the sealing element becomes denser or more compressed following long use of the device.

In order to facilitate the entrance of air into the rear end of the cylinder during a return stroke of the piston, I provide an inlet port I! in the closed end of the cylinder, this port being controlled by a check valve H3 in the form of a ball.

The cylinder is provided with tangential tubular legs [9 and 20 arranged in pairs and crosswise of the cylinder. The pair of legs l9 at the rear end of the cylinder are longer than the legs 20 which are near the front 'end. Consequently,

when the free ends of the legs, all of which project from the same side of the cylinder, are set against a door A, with the cylinder in a horizontal position and the valve stem 8 projecting past the rear edge of the door, the cylinder lies at an angle to the plane of the door and the free end of the piston rod approaches much closer to that plane than it would if the axis of the cylinder were parallel to the door. With this arrangement, the free end of the piston rod is brought closer to the hinge axis of th door than it would be if it were parallel to the door, making it unnecessary that the piston rod travel through any considerable distance across the face of astop element after once having been brought into contact with the latter.

Furthermore, the leverage through which the usual door spring acts to drive the piston back is greater than in the case of prior devices.

Instead of allowing the end of the piston rod to strike the actual door frame or casing, I secure a little shoe 2|, best shown in Figs. 1 and 5, to the door frame B in the path which must be traversed by the free end of the piston rod during the time a checking action is to be exerted. In actual practice, this shoe or block may be less than an inch long. Also, by making the shoe or block in the form of a wedge upon the thin end of which the end of the piston rod enters first, the piston is pushed back faster than would otherwise be the case by means of the thrust of the piston rod, while the door remains closed, is against a surface at right angles thereto, so that there is no binding effect on the piston. For the purpose of permitting the piston rod to ride smoothly and noiselessly across the face of the stop plate or shoe, its end is rounded or provided with a ball, as indicated at 22.

In actual practice there is never any failure of my device to produce an effective braking action, regardless of how dry the leather packing may be; this being due to the presence of the floating disk or follower which forcibly expands the annular packing element against the surrounding cylinder wall, during working strokes of the piston, but releases the pressure of the packing against the cylinder wall during return strokes.

While I have illustrated and described with particularity only a single preferred form of my invention, I do not desire to be limited to the exact structural details thus illustrated and described; but intend to cover all forms and arrangements which come within the definitions of my invention constituting the appended claim.

I claim:

The combination with a cylinder containing a piston having on one side a hub and a loose, flexible annular peripheral packing element projecting from the aforesaid side: of a short sleeve loose on the hub and free to move lengthwise on and off the hub, a thin, stiff disk loose on the sleeve and adapted to expand said packing element into engagement with the surrounding cylinder wall when the disk is pushed along the sleeve toward the body of the piston, said sleeve having a peripheral flange at its outer end to prevent the disk from slipping off, and a spring engaged at one end with the outer end of said sleeve and at the other end with one end of the cylinder to hold the sleeve on the hub and tend constantly to keep the piston in the opposite end of the cylinder.

PAUL F. KOCH. 

